linux-kernel - Re: [patch V4 part 3 10/29] x86/idtentry: Provide macros to define/declare IDT entry points

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Date:   Sun, 10 May 2020 17:58:14 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 3 10/29] x86/idtentry: Provide macros to
 define/declare IDT entry points

On Tue, May 5, 2020 at 7:15 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Provide DECLARE/DEFINE_IDTENTRY() macros.

Acked-by: Andy Lutomirski <luto@...nel.org>

except:

>
> DEFINE_IDTENTRY() provides a wrapper which acts as the function
> definition. The exception handler body is just appended to it with curly
> brackets. The entry point is marked notrace/noprobe so that irq tracing and
> the enter_from_user_mode() can be moved into the C-entry point.

"noinstr", perhaps?  I'm guessing you write this text before noinstr happened.

Also, would it perhaps make sense in the future to include the
idtentry macro somehow (via inline asm or gcc options) so that
DEFINE_IDTENTRY() could emit the stub instead of leaving it to
DECLARE_IDTENTRY()?  It might end up too messy in practice, I suppose.
This is obviously not worth changing right now, but maybe down the
road.